Remotely controlled antenna tuning and loading system



April 25, 195o v. H. VOGEL 2,505,511 REMOTELY CNTROLLED ANTENNA TUNING AND LOADING SYSTEM Filed Nov. 8, 1948 "2 IN VEN TOR. ff 4 Kf/P/VU/V V04 Patented Apr. 25, 195@ UNITED recaen REMOTELY CONTROLLED ANTENNA TUNING AND LOADING SYSTEM Vernon H. Vogel, Minneapolis, Minn., assignor to Collins Radio Company, Cedar Rapids, Iowa, a

corporation of Iowa Application November 8, 1948, Serial No. 58,835

(Cl. Z50-7) 15 Slaims. 1

This invention relates to resonating systems and more particularly it relates to the automatic tuning and loading of high frequency circuits which are to operate in resonance.

A principal object of the invention is to provide an improved arrangement for remotely and automatically tuning the antenna circuit of a radio transmitter which is supplied from a wave transmission feeder line, providing a constantl power output into the antenna circuit over a relatively wide operating antenna frequency.

Another object is to provide an arrangement for automatically tuning respective input and load circuits in successive steps while preservng the proper impedance relations during the successive steps.

Another object is to provide a simpliiied resonance discriminator arrangement for the automatic tuning or resonating of a plurality of coacting high frequency circuits.

A feature of the invention relates to an antenna system having means to adjust the loading of the antenna circuit, and separate means to resonate the coupling circuit between the antenna and a feeder line, and wherein special means are provided for maintaining the proper impedance relations between the coupling circuit and the line while the antenna is efiectiveiy decoupled from the line.

Another feature relates to the combination oi an input wave transmission feeder line connected to a tunable terminating network designed to opcrate with a predetermined Q; the network being adjustably coupled to a tuned load, for eX- ample an antenna circuit which itself has adjustable loading unit; and automatic means are provided for first tuning the terminating network` to resonance while enectively decoupling the said network from the antenna and at the same time automatically maintaining the Q of the. terminating network. Thereafter, the antenna is auto- Inatically resonated and the coupling device automatically set to a predetermined'coupling position, the foregoing operations being controlled by a simpliiied resonance discriminatori' oi the dual electron tube type.

A further feature relates tothe novel organi- Zation, arrangement and relative interconnection of parts which cooperate to provide improved and simplified automatic resonating arrangement between a feeder line and a radio antenna.

Other features and advantages not specically enumerated, will be apparent after a ccnsidera tion of the following detailed descriptions and the appended claims.

In the drawing,

Fig. i is schematic wiring diagram o1 an automatic tuning or resonating system according to the invention.

Figs. 2, 3, and 4 are respective vector diagrams explanatory of the operation system of Fig. 1.

Referring to Fig. l, the block I represents any well-known source of high or radio frequency waves, such for example as the output of the iinal amplifier of a radio transmitter. The output waves are applied to a wave transmission line 2, for example oi the coaxial type, and thence to a terminating network 3, which is arranged to be adjustably coupled by means of a coupling unit Il, to the antenna circuit 5. The unit 3 comprises a series resonant circuit including the adjustable tuning condenser t and the inductance coil 'l having a tap 8 adjacent one end to develop a voltage E1. The adjustable element of condenser 6 is connected mechanically to the armature of a reversible electric motor 9. The unit 4 comprises an adjustably mounted antenna coupling coil l@ whose inductive coupling relation with respect to coil l can be adjusted by means of a reversible electric motor l l. The antenna circuit 5 includes the tunable inductance coil I2, whose adjustable element is connected to the reversible electric motor i3. Associated with the foregoing units is a resonance discriminator unit it including a polarized differential relay l5, which controls the direction of rotation of motors 9 and It, in the manner to be described. The resonance discriminator i4 also includes a pair of gridcontrolled electron tubes i6, Il, which may be of any well-known type. The plates I8, IS, of these two tubes are excited in phase and in parallel by a portion oi the energy received from line 2. The cathodes 2&3, 2|, are each connected to ground through a respective winding 22, 23, of the relay l5. The relay i5 is preferably of the neutral polarized differential type having an armature ill and a pair of contacts 25, 25. When both windings t2, 23, are decnergized, or if they are energized equally, the armature @All assumes a neutral position with respect to the associated contacts 2.5, 2e. This condition therefore prevails when the anode-cathode current of tube l5 is equal to the anode-cathode current of tube Il. If however, the anode-cathode current of either tube predominates over that of the other tube, the relay l5 will be correspondingly energized and will move its armature 2d in either direction, depending upon which winding is predominantly energized.

The discrminator unit i4 operates upon the principle that the control grids 21, 28, are always 180 out of phase, and for this purpose there is provided an additional inductance coil 29, which is tightly coupled with the coil 1. In fact, if desired, the coils 1 and 29 may be a single continuous winding with the midpoint of coil 29 connecte-d to ground as shown. One end of coil 29 is connected by conductor 30 to grid 21 and the tap on coil i is connected by conductor 3i to grid 23. In other words, the grids 21 and 28 are aln ways excited by the wave energy from line 2 to equal amounts but in phase opposition. If, for example, the voltage applied to the plates le and I9 is represented by E3; the voltage to grid 28 is represented by Ei; and the voltage to grid 21 is represented by E2, then when the unit 3 is in resonance the vector` relations between these three voltages are as indicated in Fig. 2.

Connected in series with the transmission line 2 and unit 3 is a non-inductive resistor 32, whose resistance is made equal to the characteristic impedance of the line 2, so that standing waves are minimized and the terminating network 3 presents the proper operating Q to the transmission line during that stage in the automatic resonating of the system when the antenna is decoupled from unit 5, as will be described. Howe ever, when the antenna circuit is being automatically loaded by coil I2 and motor I3, the resistor 32 is automatically short-circuited by a switch 33 as will be described. Preferably, although not necessarily, the -discriminator tubes IS and i1 are arranged so that the ratio of gridto-plate voltages is comparable to the mu or ampliiication factor of each tube, so that the rectified grid currents of these tubes are small as compared to the rectiiied plate currents, and so that grid circuit variations reflect only slightly into the current flowing through the respective windings 22, 23. Associated with the various units described above, is a three-position fivegang switch 3F., having ve ganged movable switch arms 35, 3S, 31, 38, 39, with a common stepping magnet lio and with associated stationary contacts 35a., 3517, 35e; 36a, 36D, 35e; 31a, 32h, 31o; 38a, 38h, 38e; 39a, 39h, 3Sc. Motor Il also rotates a switch operating cam M which controls the switch contacts 42, 43.

The motors il, Il and is may be of the shaded pole type, each having its eld windings 9a, Ila, 13a, continuously energized from the 110 volt alternating current supply terminals t4, 45, and each having respective right-hand and left-hand phase windings or shading coils 9b, 2c; lll), lic; l3b, l3c. When, for example, a left-hand shading coil is short-circuited, the corresponding motor runs in a clockwise direction; if the righthand shading .coil is short-circuited, the motor runs in a counter-clockwise direction. When neither shading coil is short-circuited, the motor stops rotating. The circuit for energizing the winding it of the switch stepping magnet il is controlled by the normally closed contacts se,

4.3, of a manually operable. reset key 50, and by 6 the contacts 5.1 of. relay 52.. When relay a2 is deenergized, its contacts are, closed, thus closing a circuit for the stepping magnet. e6, traceable from battery 52, reset contacts, 4B, 48 contacts 5I toy ground at 5d. The sha-.ding coilsv of the. motors have, transformer action with regard to the motor primaries im, lla, i3d, andtherefore develop a voltage across the shading windings. As either one of these windings is connected across a load, such4 as the coil. 52 a. current will ow in this coil and in this case, if coil 52 has a low impedance compared to the shading windings the motor will operate with very little loss in efciency and the relay 52 will be energized and operate its armature. Therefore, relay 52 has an operating circuit whose voltage source is the appropriate shading coil of the motor.

When energized, the stepping magnet operates in the following manner: the armature 4E! rotates a ratchet to which are attached the switch rotors 35-39. When the coil de of the stepping relay is de-energized, the actuating arm on i0 slips back on the ratchet with the moving switch sections 35-39, remaining in the previous position. It should also be pointed out that when the stepper is in position C and is again advanced, it will rotate again to position A and start the cycle over again.

`When the stepping switch is in. position #1, that is with the brushes 35-39 in engagement with contacts 35o-39a, the system is in condition to test and automatically adjust the tuning of unit t. At the same time, the antenna coupling coil Sii is eiectively decoupled at the normally open contacts 55, of relay 51. In position #2, the relay 51 operates to couple the antenna circuit 5 to unit 3 by means of coil Il), and the coil i2 is automatically adjusted to tune the antenna circuit. In position #3, the coil i2 and the coil iii remain under control of motors I3 and li so that correction can be automatically maintained for variations in the reactance and resistance existing at the end of line 2. Thus, the stepping switch remains in position #8 until a new fren quency of transmission is being used, whereupon reset key E9 can be manually operated to restart the automatic tuning and antenna loading cycles.

For purposes of explanation, it will be assumed that key 5i! has been momentarily operated for a new transmission frequency to be supplied over the line 2. Therefore, a circuit is traceable from battery 53, stepping magnet 66' to ground at key 5t. This immediately advances the brushes of the stepping switch from position #8 to position #1. If the unit 3 is in resonance at the new frequency, the voltage and current developed across the line 2 are in phase, and the voltages Ei and E2 are in quadrature with voltage E3 from the line. This condition is represented vectorially in Fig. 2 of the drawing. Thus, the grids 21 and 23 are excited equally and tubes IG, l'l, conduct equally. As a result, windings 22 and 23 are equally energized and the armature 24 remains in neutral position.

If however, the reactance of coil 'l is greater than the reactance of condenser 6, as represented by the vector diagram of Fig. 4, tube l1 will conduct more than tube I6, and armature 24 will close with contact 26. If however, the reactance of coil 'i is less than the reactance of condenser 6, tube E6 will conduct to a greater extent and armature 2li will engage contact 25.

In order tol measure the radio frequency voltage across thel terminating load for the line 2, there is provided a diode 58 whose anode 59 is coupled tov the load. through condenser 60, and whose cathode 6I is connected through an ad justable resistance: 62, to one winding 53, of a neutral diiferential polarized relay 64.. The other winding E5. of this relay is steadily energized by battery G6. The rectified radio frequency energy flowing through winding 63 is thus balanced against the current through winding 65. The rectified voltage that is thus measured can be controlled byyvarying resistance 62; In other Words, the winding `65 can be energized to a.

predetermined extent representing a predetermined radio frequency voltage across the load, and the resistance 62 can be adjusted so that when the system is in proper adjustment at the new frequency, the rectied signal through winding 62 balances the current through winding 65. A radio frequency choke coil 61 provides a D. C. return path to ground for the diode 58; and the condenser 68 by-passes the radio frequency energy to ground before it can pass through the winding 63.

With the stepping switch in position #l as above described, the circuit of relay 51 is open at contact 31o, thus effectively decoupling the antenna circuit 5 from unit 3. Depending upon the relative magnitudes of the reactance of elements 6 and 1, the relay l 5 will be selectively operated. If the relative magnitudes are such that the armature 24 is operated to engage contact 25, a circuit is traceable from ground 54, through relay winding 52, armature 24, contact `25, brush 36, contact 36a, winding 9c of motor 9, thus rotating the condenser 6 to resonate the unit 3. Thus the motor 9 rotates the condenser in the appropriate direction until resonance is obtained, whereupon armature 24 again assumes its neutral position. In this position, the circuit of relay '52 is broken and contacts 5I close to complete the circuit for stepping magnet 46, thus advancing the stepping switch to position #2.

It should be observed that during the rst tuning operation in position #l of the switch,

motor I I rotates the coupling coil Ill with respect e to coil 1 until the switch contacts 42, 43, are opened, thereby stopping the rotation of motor II. The cam 4I is so oriented that a predetermined value of coupling between coils I9 and 1 can be obtained. The degree of this coupling depends upon the resistance and reactance of the antenna, but it is not critical over a fairly wide range such as around one-quarter wave point. It is necessary that a certain amount of coupling be maintained between coils IIJ and 1 since the,

operation of the discriminator depends upon the reflected reactance from the antenna circuit into coil 1. The formula for reflected reactance which is equal to formula whereas around the half wave point, these values may be up inthe thousands. This makes it necessary to adjust this coupling to a predetermined value which predetermined value must vary with theantenna used.

With the switch in position #2, the discriminator I4 now shifts its control from motor 9 to motor I3. In position #2, relay 51 operates over a circuit traceable from ground through the winding of relay 51, contacts 31o, 31h, switch arm 31 to grounded battery. Relay 51 when operated reconnects the coupling coil I0 in circuit with TIS the antenna circuit. Because of the mutual coupling between coils I0 and 1, the reactance from the antenna and its associated elements will be reflected into coil 1, and thus will disturb the previous resonance phase condition existing between voltages Ei and E2. This off-resonant condition again causes the appropriate one of the tubes I6, I1, to be predominantly conductive and therefore selectively determines the rotation of motor I3. It should be observed that in position #2 of the stepping switch, the contacts of relay I5 are connected to the #2 contacts 35h, 36h, and thence to the shading coils of motor I3. Motor I 3 therefore rotates the adjustable element of coil I2 in the proper direction until the antenna circuit 3 is in resonance. The amount of mutual coupling required between coils I0 and 1! is a function of the "Q of the antenna circuit, since the reflected reactance depends on the Q" of that circuit. When the antenna circuit has thus been tuned to resonance, armature 24 again. restores to neutral position, thereupon releasing the relay 52 and reclosing the circuit of the step-` per magnet 46, thus advancing the stepping magnet to position #3. Y

It will be noted that in position #3, the shading coil of motor I3 still remains under control of the discriminator I4 by reason of the strap connection between contacts 35h, 35o, and 36h, 36e. In position #3 of the switch, a circuit is closed for winding 61 of switch33, this circuit being traceable from ground, through Winding 61, contact 38o, brush 38 to grounded battery 68. When switch 33 is thus operated, it short-circuits the resistance 32 and grounds contact 5I of relay 52 so that when the differential relayv 24 returns in neutral position, it cannot advance stepper relay 46". This is necessary to prevent the stepper from advancing and going through the complete tune-up cycle again. In position #3, the motor II is placed under control of the relay 64 in the radio frequency voltage measuring circuit. 1f the rectified radio frequency voltage is below the value corresponding to the desired loading con- -1 dition of the system, the winding 65 of relay 64 will take control and cause armature 69 to engage contact 10, thus closing a circuit traceable from ground, brush 39, contact 39o, armature 69, contact 10, winding IIb to ground. Motor II therefore again rotates the coil I6 in the proper direction to bring the rectified radio frequency voltage up to a point where it balances the steady current through winding 65. If however, the radio frequency voltage had been above the predetermined value corresponding to the desired loading, the winding 63 would have been predominantly energized and the winding Ila would have been short-circuited, thus rotating the coil I6 in the opposite direction. In either case, the coil III is rotated to correspond with the predetermined voltage condition that is required at the input to the-unit 3. This voltage will of course be the voltage that is developed across the end of the line 2, where it feeds the unit 3 and will be equal to the characteristic impedance of the line. This resistance will consist of the lost resistance of coil 1 and the reflected antenna load resistance. When the foregoing operations have been thus automatically completed, the

. parts remain in their last set position and with the stepping switch in positionv #3, so that the. system provides a. continuous check and correction for any further variations in the reactance and resistance occurring at the end of the line 2 as it feeds the unit 3.

While certain speclcfemb'odimentshavebeen described herein, it vwill bei understood that var-4 ions changes and modificationsv may be made thereiniwithout departing from the spirit and scope of the invention.

What is claimed is:

l. In a wave transmission system having first and second sections arranged to be automatically' adjusted to' resonance, arresonance adjust ing' member for each section, a rst motor for opera-ting the member of the first section, a second motor for'operating the member of the second section, adjustable coupling means between said sections, a resonance discriminator common to saidsectio'ns, a third motor' for automatically operating said coupling means, an impedance representing'the equivalent loading of the second section on the rst' section when said iirst and second sections are coupled, means including said discriminatorl and said nrst motor to tune the first section to resonance while automaticallyv inserting said impedance in circuit with the iirst section and" while the' said sections are decoupled, and means including saiddi'scriminator and said second motor for automatically tuning', the second section to resonance while deleting iinpedance'.

2. A wave transmission system according to claim 1 in which means" are provided for operating said third motor to increase the coupling between said sections while said second section is being tuned to resonance.

3. A wave transmission system according to claim 1 in which said discriminator includes a relay which controls the direction of rotation of said first and second motors.

4. A wave transmission system according to claim i in which said discriminator includes a relay which controls the direction of rotation of said rst and second motors, andv separate switch means are provided for controlling the direction of rotation of said third motor'.

5. A wave transmission system according to claim 1 in which said discriminator includes a relay which controls the direction of rotation of said rl'rst and second motors, and a second relay for controlling the direction of rotation of said third motor, said second relay being operated independently of the -rst relay.

G. A system according to claim' l in which said first section comprises a tuning condenser connected in series with said impedance, the adjusting member of said condenser being connected to said first motor.

'7. A system according to claim 1 in which said first section includes a tuning condenser connected in series with said impedance and a coupling coilV which coil is coupled to said adjustable coupling means, the said condenser having its adjusting member connected to said rst motonand said second section includes an ad- Jiist'able inductance connected in series with said coupling means and having its adjusting member connected to said second motor.

8l A wave transmission system according to` in which said discriminator includes aj claim l relay which controls the direction of rotation of said first and second motors,

QL In a wave transmission system having a first third driving motor for' controlling the coupling of said sections, a resonance discrmina'tor com- "mon to saidsections', means: including said third motor to effectively decouple: said sections while inserting an equivalent impedance in circuitk between said source and said first' section, means including said discrirninator and said rst" motor for automatically tuning said first sectionv to resonance while said sections are decoupled, and means including said discriminator and said second motor for automatically'tuning said second section and also increasing the coupling between said sections.

lo. In a wave transmission system, a source of high frequency waves, a wave transmission line connected at one end to said source, a tunable network terminating the other end of said line; said network having rst and second tunable sections coupled by an adjustable coupling element, said networkliaving a predeterminedv Q when said sections are tuned to resonance and when they are coupled to a predetermined degree, means for automatically decoupling said sections and for automatically inserting an impedance to maintain said Q, means for automatic-ally tuning said first section to resonance while decoupled' from the second section and while maintaining the insertion of said impedance, and means for automatically tuning said second section to resonance while maintaining impedance deleted, and while increasing the coupling between said sections.

ll. A wave transmission system according to claim lil, in which the said' means for automatically tuning said iirst and second sections includes a resonance discriminator and a pair of motors respectively for the tuning elements of said sections, said resonance discriminator including a selectively reversible relay switch which is successively associated with said motors to control their direction and duration of rotation..

i2. In a wave transmission system, a circuit to be automatically tuned to resonance with a source, a pair of grid-controlled tubes, means coupling the grids of said tubes to said circuit so that the grids are excited in opposite phase, means to excite the anodes of said tubes in like phase from said source, a motor for moving the resonance adjusting element of said circuit, and a relay selectively controlled by the differential: anode-cathode currents fromsai'd tubes to cause said motor to operate until said circuit is tuned to resonance, said circuit including an inductance coil having a point intermediate its ends oonnected to the grid of one tube, and another inductance coil coupled to said rst coil and having one end connected to the grid of the other tube.

13. In a wave transmission system, a circuit to be automatically tuned to resonance `with a source, a pair of grid-controlled tubes, means coupling the grids or said tubes to said circuit so that the grids are excited in opposite phase, means to excite the anode; of said tubesl in like phase from said Isource', a motor for moving the resonance adjusting element of said circuit, and" ay relayv selectively controlled by the differential' anode-cathode currents from said tubes to cause said motor to operate unil said circuit' is tuned to resonance, said circuit including an inductancc'- coil connected in series between said line and ground, a point intermediate the ends of said coil connected tothe grid of one' tube, another: coil;

second tuned circuits to be resonated with a source, each of said sections having an individual tuning element, a first motor for said rst element, a second motor for said second element, a third motor for controlling the coupling of said sections when the rst section is being tuned to resonance and when the second section is being tuned to resonance, a resonance discriminator comprising a pair of grid-controlled electron tubes having their grids excited in opposite phase from said first circuit and their plates excited in like phase from said source, a three-position stepping switch effective in one position to control the rst motor in response to the differential current from said tubes and effective in a second position to control the second motor in response to the diiTerential current from said tubes, and circuits for automatically stepping said switch as each resonant condition is automatically reached,

said tubes having their anode-cathode circuits 20 differentially connected to the windings of a neutral polarized relay, said relay having contact 10 sets for controlling the direction of rotation of the rst and second motors, other relay means for controlling the direction and rotation of the third motor.

15. A wave transmission system according to claim 14 in which an equivalent non-inductive resistance is connected in series between the source and said rst section, and a switch device is controlled by said third motor for shunting said resistance when the said second circuit is being adjusted to resonance.

VERNON H. VOGEL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,376,667 Cunningham et a1. May 22, 1945 2,417,191 Fox Mar. 11. 1947 2,449,174 OBrien Sept. 14, 1948 

